original development tree for Linux kernel GTP module; now long in mainline.
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/*
* linux/fs/sysv/dir.c
*
* minix/dir.c
* Copyright (C) 1991, 1992 Linus Torvalds
*
* coh/dir.c
* Copyright (C) 1993 Pascal Haible, Bruno Haible
*
* sysv/dir.c
* Copyright (C) 1993 Bruno Haible
*
* SystemV/Coherent directory handling functions
*/
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/swap.h>
#include "sysv.h"
static int sysv_readdir(struct file *, struct dir_context *);
const struct file_operations sysv_dir_operations = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.iterate = sysv_readdir,
.fsync = generic_file_fsync,
};
static inline void dir_put_page(struct page *page)
{
kunmap(page);
page_cache_release(page);
}
static inline unsigned long dir_pages(struct inode *inode)
{
return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}
static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
{
struct address_space *mapping = page->mapping;
struct inode *dir = mapping->host;
int err = 0;
block_write_end(NULL, mapping, pos, len, len, page, NULL);
if (pos+len > dir->i_size) {
i_size_write(dir, pos+len);
mark_inode_dirty(dir);
}
if (IS_DIRSYNC(dir))
err = write_one_page(page, 1);
else
unlock_page(page);
return err;
}
static struct page * dir_get_page(struct inode *dir, unsigned long n)
{
struct address_space *mapping = dir->i_mapping;
struct page *page = read_mapping_page(mapping, n, NULL);
if (!IS_ERR(page))
kmap(page);
return page;
}
static int sysv_readdir(struct file *file, struct dir_context *ctx)
{
unsigned long pos = ctx->pos;
struct inode *inode = file_inode(file);
struct super_block *sb = inode->i_sb;
unsigned long npages = dir_pages(inode);
unsigned offset;
unsigned long n;
ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
if (pos >= inode->i_size)
return 0;
offset = pos & ~PAGE_CACHE_MASK;
n = pos >> PAGE_CACHE_SHIFT;
for ( ; n < npages; n++, offset = 0) {
char *kaddr, *limit;
struct sysv_dir_entry *de;
struct page *page = dir_get_page(inode, n);
if (IS_ERR(page))
continue;
kaddr = (char *)page_address(page);
de = (struct sysv_dir_entry *)(kaddr+offset);
limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
char *name = de->name;
if (!de->inode)
continue;
if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
fs16_to_cpu(SYSV_SB(sb), de->inode),
DT_UNKNOWN)) {
dir_put_page(page);
return 0;
}
}
dir_put_page(page);
}
return 0;
}
/* compare strings: name[0..len-1] (not zero-terminated) and
* buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
*/
static inline int namecompare(int len, int maxlen,
const char * name, const char * buffer)
{
if (len < maxlen && buffer[len])
return 0;
return !memcmp(name, buffer, len);
}
/*
* sysv_find_entry()
*
* finds an entry in the specified directory with the wanted name. It
* returns the cache buffer in which the entry was found, and the entry
* itself (as a parameter - res_dir). It does NOT read the inode of the
* entry - you'll have to do that yourself if you want to.
*/
struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
{
const char * name = dentry->d_name.name;
int namelen = dentry->d_name.len;
struct inode * dir = dentry->d_parent->d_inode;
unsigned long start, n;
unsigned long npages = dir_pages(dir);
struct page *page = NULL;
struct sysv_dir_entry *de;
*res_page = NULL;
start = SYSV_I(dir)->i_dir_start_lookup;
if (start >= npages)
start = 0;
n = start;
do {
char *kaddr;
page = dir_get_page(dir, n);
if (!IS_ERR(page)) {
kaddr = (char*)page_address(page);
de = (struct sysv_dir_entry *) kaddr;
kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
for ( ; (char *) de <= kaddr ; de++) {
if (!de->inode)
continue;
if (namecompare(namelen, SYSV_NAMELEN,
name, de->name))
goto found;
}
dir_put_page(page);
}
if (++n >= npages)
n = 0;
} while (n != start);
return NULL;
found:
SYSV_I(dir)->i_dir_start_lookup = n;
*res_page = page;
return de;
}
int sysv_add_link(struct dentry *dentry, struct inode *inode)
{
struct inode *dir = dentry->d_parent->d_inode;
const char * name = dentry->d_name.name;
int namelen = dentry->d_name.len;
struct page *page = NULL;
struct sysv_dir_entry * de;
unsigned long npages = dir_pages(dir);
unsigned long n;
char *kaddr;
loff_t pos;
int err;
/* We take care of directory expansion in the same loop */
for (n = 0; n <= npages; n++) {
page = dir_get_page(dir, n);
err = PTR_ERR(page);
if (IS_ERR(page))
goto out;
kaddr = (char*)page_address(page);
de = (struct sysv_dir_entry *)kaddr;
kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
while ((char *)de <= kaddr) {
if (!de->inode)
goto got_it;
err = -EEXIST;
if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
goto out_page;
de++;
}
dir_put_page(page);
}
BUG();
return -EINVAL;
got_it:
pos = page_offset(page) +
(char*)de - (char*)page_address(page);
lock_page(page);
err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
if (err)
goto out_unlock;
memcpy (de->name, name, namelen);
memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(dir);
out_page:
dir_put_page(page);
out:
return err;
out_unlock:
unlock_page(page);
goto out_page;
}
int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
{
struct inode *inode = page->mapping->host;
char *kaddr = (char*)page_address(page);
loff_t pos = page_offset(page) + (char *)de - kaddr;
int err;
lock_page(page);
err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
BUG_ON(err);
de->inode = 0;
err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
dir_put_page(page);
inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
mark_inode_dirty(inode);
return err;
}
int sysv_make_empty(struct inode *inode, struct inode *dir)
{
struct page *page = grab_cache_page(inode->i_mapping, 0);
struct sysv_dir_entry * de;
char *base;
int err;
if (!page)
return -ENOMEM;
err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
if (err) {
unlock_page(page);
goto fail;
}
kmap(page);
base = (char*)page_address(page);
memset(base, 0, PAGE_CACHE_SIZE);
de = (struct sysv_dir_entry *) base;
de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
strcpy(de->name,".");
de++;
de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
strcpy(de->name,"..");
kunmap(page);
err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
fail:
page_cache_release(page);
return err;
}
/*
* routine to check that the specified directory is empty (for rmdir)
*/
int sysv_empty_dir(struct inode * inode)
{
struct super_block *sb = inode->i_sb;
struct page *page = NULL;
unsigned long i, npages = dir_pages(inode);
for (i = 0; i < npages; i++) {
char *kaddr;
struct sysv_dir_entry * de;
page = dir_get_page(inode, i);
if (IS_ERR(page))
continue;
kaddr = (char *)page_address(page);
de = (struct sysv_dir_entry *)kaddr;
kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
for ( ;(char *)de <= kaddr; de++) {
if (!de->inode)
continue;
/* check for . and .. */
if (de->name[0] != '.')
goto not_empty;
if (!de->name[1]) {
if (de->inode == cpu_to_fs16(SYSV_SB(sb),
inode->i_ino))
continue;
goto not_empty;
}
if (de->name[1] != '.' || de->name[2])
goto not_empty;
}
dir_put_page(page);
}
return 1;
not_empty:
dir_put_page(page);
return 0;
}
/* Releases the page */
void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
struct inode *inode)
{
struct inode *dir = page->mapping->host;
loff_t pos = page_offset(page) +
(char *)de-(char*)page_address(page);
int err;
lock_page(page);
err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
BUG_ON(err);
de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
dir_put_page(page);
dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(dir);
}
struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
{
struct page *page = dir_get_page(dir, 0);
struct sysv_dir_entry *de = NULL;
if (!IS_ERR(page)) {
de = (struct sysv_dir_entry*) page_address(page) + 1;
*p = page;
}
return de;
}
ino_t sysv_inode_by_name(struct dentry *dentry)
{
struct page *page;
struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
ino_t res = 0;
if (de) {
res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
dir_put_page(page);
}
return res;
}